Method of making offset color plates



Patented June 24, 1924.

UNITED STATES P'ATENT OFFICE.

LAVANT V. CAUKIN, OF MENASHA,

WISCONSIN, ASSIGNOR TO MENABHA PRINTING & CARTON 00., OF MENASHA, WISCONSIN,

A conrona'rion or WISCONSIN.

METHOD or naxmo orrsm' coLo-n rm'r'ns.

Ho Drawing.

To all whom it may concern.

Be it known that I, LAvAN'r V, CAUKIN, a citizen of the United States, residing at Mena'hha, in the county of Winnebago and State of Wisconsin, have invented a certain new and useful Im rovement in Methods of Making Ofiset Co or Plates, of which the following is a specification. Off-set printing occupies a very importantfield 1n the printing art, but the production of its necessary color plates has been a very serious problem and at times prohibitive, this because, as heretofore commerciall practiced, it has been necessary to use rom six to ten or more colors to reproduce the colors of a given picture, each of these colors requiring a separate printing plate and a large amount ofre touching or hand manipulation which in turn destroys the accuracy of the copy as compared with the original picture.

The object of this invention is to make ofi-set color plates which are so absolutel accurate in reproducing the original copy that as good results can be obtained with four, or even three, eight under the old methods, and to produce these plates at a cost per plate materially below that of the prior art. f

-The invention consists in a methodjof attaining foregoing and other obie'cts,

which willhe hereafter more fully set orth in the specification and claims.

Assume that a given'm ltiple colored picture is to be reprodu this. ;invention, It is so an assuming'jour co in thefinished produc half-tone negatives corresponding, respectively, to the colors of yellow-, red, blue and black, are ,made of it .bylis tandard photo,- engraving methods. A'fprint ,of each of these four negatives is 'cofiv: ntionally made on a separate cooper plate and etched in the ordinary. manner., This set-df'fplates is then used seriall in the ordinary photoengraving meth tasuperimpose one color upon the other in the r 'Iar standard order to produce one proo ,oi the combinabefore a camera are to he used tion of the colors the differ-f ent plates; in other we! ple of the produced in the commercial printing; This compositecolor proof is sent to the customer for approval as to whether the finished to make a sam- -or proofs submitted plates as with six to the method of our conventional final product which is tobev Application filed March 11, 1923. Serial No. 625,879.

product shown by it is satisfactory. If the customer calls for any changes, they are made upon the separate plates by old, wellknown methods and anew composite proof to the customer until iven. The steps down 0 d and in'present use his final approval is to this point are and the plates could be conventionally used for letter-press printing which is, however, much more expensive than off-set printing. In order' to adapt these half-tone color plates for use in off-set printing with the same physical results as though they were used in letter-press printing while producing the ofi-set plates at a very great saving in expense over the old methods heretofore used in producin following procedure 0 followed:

After the product sample has been approved by the customer, a proof is made of each plate in its own color for the use hereafter described. An ordinary black ink proof is pulled; from each plate on very white double-coated enamel paper-such, for instance, as De J onge paperwhich will give in the roof an accurate showing of all details 0 the copper plate. Whatever paper is used must be tough and nonstretchable in orderto insure register of the lates later produced from these proofs.

avin obtained these accurate black and white proofs, a camera is set up where it is substantially absolutely free from vi-' bration; each of the black and white proofs this invention is oil-set plates, the

placed in succession in exactly the same spot on the copy board before the camera, so mounted that it cannot be moved between photographs of the successive plates- {this to insure a perfect register of the lodion, instead of one in accordance with conventional practice, just before its emersion in the conventional silver bath,- one coating of collodion being drained from one side (or end) of the glass, the other coating applied while the first coating is still tacky, being a plied and drained from the opposite side or end) of the glass.

Having obtained a set of wet plate negamethod reduces the cost tives-preferably on these double collodion coated plates-one for each color which is to be used in making the final finished work, the negatives, each accompanied by th proof in its own color, taken from its own copper plate as heretofore described, is turned over to a commercial lithographcr who proceeds by conventional methods to print these plates one at a conventional lithographers metal. The lithographer uses the colored proofs furnished him'as just described to guide him in the amount of ink he uses on the plates as he runs them so that the finished prod "ucts will correspond with the proof previously approved by the customer. Owing to the fact that most printers black inks contain a large amount of blue pigment,

invisible to the eye but very visible to a camera, best results are obtained in making the so-called black proofs, heretofore referred to, by adding to the commercial ink with which the black proofs are made approximately 5% in volume of yellow ink and 5% in volume of red ink and thoroughly mixing it in. This result is still apparently black ink but the product is much more dense in color for the camera to pick up, with the result that much sharper ima es will be reproduced on the negatives w ich go to the lithographer.

Attention is again called to the urgent desirability of doing the photographing of the half-tone copper plate proof where substantially no vibration takes place. If this instruction is not adhered to, the photographs will not be accurate in tone value, and the finished printing will be correspondingly defective.

In actual commercial work the described of producing the plates required for a given piece of work from fifty to sixty-five er cent.

The use of the sing e color proofs from the original half tone plates in chec 'ng the inking ofthe final lithographic-offset color plates is quite im ortant because the rinter can, by materia y varying the inkmgof a single offset color plate, materially distort the color-in of the finished product and perhaps entire y destroy its ut lity.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. The herein-described method of producing ofi-set color plates consisting in first making conventional half-tone plates of the picture to be reproduced, one for each color time onto any entering into the finished product, which when tested in combination by conventional methods produce the desired finished product; taking an accurate black and white roof from each plate, making accurate full etail re istering negatives of the respective black an white proofs, and then conventionally using said negatives to produce conventional lithographic plates thereof.

2. The herein-described method of producing offset color plates consisting in making conventional half-tone plates of the picture to be reproduced, one for each color entering into the finished product, which when tested in combination'by conventional methods produce the desired finished product; taking an accurate black and white proof from each plate; making accurate, full detail, registering, wet plate double collodion coated negatives of the respective black and white proofs, and then conventionally usingsaid negatives to produce conventional lithographic plates thereof.

3. The herein-described method of producing off-set color plates consisting in first making conventional half-tone plates of the picture to be reproduced, one for each color entering into the finished product, which when tested in combination by conventional methods produce the desired finished product; taking an accurate black and white proof from each plate, using commercial black ink with about five per cent of red and five per cent of yellow ink, both by volume, mixed therein; making accurate, full detail, registering, wet plate double collodion coated negatives of therespective black and white proofs, and then conventionally using said negatives to produce conventional lithographic plates thereof. v

4. The herein-described method of producing offset color plates consisting in first making conventional half-tone plates of the picture to be reproduced, one for each color entering into the finished product, which when tested in combination by conventional methods produce the desired finished product; taking an accurate black and white proof from each plate on tough, nonstretchable, very white, double coated enamel paper; making accurate, full detail registering negatives of the respective black and white proofs, and then conventionally using said negatives to produce conventional 11thographm plates thereof.

In witness whereof, I

scribed my name.

LAVANT V. CAUKIN.

have hereunto sub 

